Tel Aviv, Israel — Not much is known about Supreme Court nominee Elena Kagan's views, so her praise four years ago for Israel's Supreme Court Chief Justice Aharon Barak has taken on unusual significance in the high-stakes nomination process.

Ms. Kagan reportedly called Mr. Barak a "judicial hero'' who has "best advanced the values of democracy." Sen. Jeff Sessions (R) of Alabama last week called the remarks "very troubling'' and warned it might provide "real insight into her view of the law."

Indeed, Barak, 73, is internationally renowned for pushing human rights in an insecure democracy, insisting on the primacy of secular jurisprudence despite the veneration of Jewish religious law, and for strengthening the court's check on the other branches of government. At home, he is regarded as the most influential justice in Israel's 62-year history and a figure who has revolutionized the high court's standing.

But he is also a controversial figure in Israel. Though he is lionized in legal circles, critics say he spearheaded a homogeneous court of secular elites that overstepped its bounds by promoting a universalist legal agenda out of touch with the rest of society.

Barak pushed "the belief that the court can intervene in any issue, including budget, foreign affairs, and security, which is opposite of what existed in the past…. They took powers which were not really in their hands," says Avraham Diskin, a professor of political science at Hebrew University of Jerusalem, who argues that the justice turned Israeli jurisprudence on its head.

"The degree of activism of Barak is such that he ruined the rule of law in Israel. When you go to court, nothing is clear. It’s a gamble."

Kagan walked back her remarks on Tuesday, but said, "I admire Justice Barak for what he's done for the State of Israel in ensuring an independent judiciary," Reuters reported. Her original praise for Barak came in 2006, when she was dean of Harvard Law and he got an award on campus for his work as a justice.

In three decades on the Israeli high court, Barak sought to fill Israel's constitutional vacuum by elevating "basic laws" which protect universal values – such as the right of movement, privacy, and property – into a quasi Bill of Rights for Israel that was used to strike down parliamentary laws, annoying lawmakers.

He was also more open to hearing legal petitions against government policies. He occasionally ruled on behalf of Palestinians who challenged Israel's venerated security establishment. While security hawks accused him of butting in with lofty human rights considerations that Israel could not afford, human rights activists criticized Barak of being too deferential to the military.

"Some of the court's decisions on human rights and terrorism were made at a time when others in the international community were addressing the same issues, so they seemed relevant to folks abroad," says Sari Bashi, the head of the Israeli human rights group Gisha.

"Aharon Barak deepened ties between the Israeli supreme court and legal systems abroad. He has promoted the courts use of comparative law in legal decisions," says Mr. Bashi, who also helped Barak translate one of his books into English.

A Holocaust survivor, Barak served as Israeli attorney general in the 1970s and a legal advisor to Israel's negotiating team during the Camp David negotiations with Egypt. He left the court in 2006, and his like-minded successor, Dorit Beinish, has had to face down a backlash of critics who seek to limit the Israeli courts power.

"He introduced to our legal system the idea of activist court. In American terms, this is unacceptable," said Yossi Sarid, the former head of the far-left Meretz party who called Barak a "genius." "[Republicans] are blaming Barak for having an agenda, but they have their own agenda."